Generally, in various devices, a power failure sensing device is employed broadly. For example, in a power failure sensing device shown in FIG. 6, an output voltage from an internal electrical power source 1 provided in a use apparatus is altered by a reference voltage by a regulator 2 and the reference voltage is outputted to a comparator 3. Also, as the output voltage from the internal electrical power source 1 is altered a power failure sensing voltage is created by resistors R1, R2 and the power failure sensing voltage is outputted to comparator 3.
When the output voltage from the internal electrical power source 1 falls to less than a predetermined level, a power failure sensing signal (L signal) is generated. However, for example, as a card reader is used in a cash dispenser and the like, the card reader, a subordinate use apparatus, is controlled by the host external device. In the subordinate use apparatus, when a power failure occurred in a power source of the interior side of the subordinate use apparatus, the state of the power failure of the subordinate use apparatus can be detected by the power failure sensing device as described above.
It is problematic not to be able to detect the state of a power failure when an occurrence is detected in the host external device side. That is, even if a power failure does not occur in the use apparatus itself as a subordinate device, there may be cases where a power failure occurs in the host external device side. Thus, the state of the power failure of the external device side keeps the failure at the subordinate device not detected. As a result, when an operation of the use apparatus as a subordinate device is continued, drawbacks are given to an operation of the whole device.
Accordingly, it is a object of the present invention to provide a power failure sensing device which can detect well the state of a power failure of an external device side in addition to a power failure sensing of the interior side with a simple configuration and a card reader having the power failure sensing device.